System and method for providing sip trunk service to a telephone system

1. A method of providing at least one SIP trunk service to at least one

telephone system by an application server over a network, the method comprising:

establishing a connection between the at least one telephone system and a first network entity of the network via a first access node, wherein said first network entity is a Primary Enterprise Access Session Border Controller (PR-ESBC) and is connected to the application server;

availing the at least one SIP trunk service, by the at least one telephone system via the first access node, from the application server connected to the first network entity;

checking, dynamically, by the at least one telephone system, connectivity with the first network entity via the first access node;

establishing a connection between the at least one telephone system and a second network entity of the network via a second access node wherein the second network entity is a Secondary Enterprise Access Session Border Controller (GR-ESBC), in an event the connectivity between the at least one telephone system and the first network entity via the first access node fails, wherein said second network entity is connected to the application server;

transmitting a signaling request to avail the at least one SIP service, by the at least one telephone system via the second access node, to the application server connected to the second network entity;

configuring the at least one telephone system to avail at least one SIP trunk service, via the second access node, from the application server connected to the second network entity;

processing, by the application server connected to the second network entity, the signaling request received from the at least one telephone system via the second access node;

selecting, by the application server, a domain associated with the second network entity based on an identification of error code received from the at least one telephone system; and

providing the at least one SIP trunk service, based on the selected domain to the at least one telephone system via the second access node, by the application server connected to the second network entity.

2. The method as claimed in claim 1 , wherein the first access node and the second access node are based on the Session Initiation Protocol (SIP).

3. The method as claimed in claim 1 , wherein the at least one telephone system is one of a Private Branch Exchange (PBX), a Unified Border Element (UBE) and a Unified Communications Manager (UCM).

4. The method as claimed in claim 1 , wherein configuring the at least one telephone system to avail the at least one SIP trunk service, via the second access node, from the application server connected to the second network entity further comprises executing, at the at least one telephone system, at least one of a transmission control protocol (TCP) or user datagram protocol (UDP).

5. The method as claimed in claim 4 , wherein the at least one telephone system avails the at least one SIP trunk service, via the second access node, from the application server connected to the second network entity based on the IP address of the second network entity.

6. The method as claimed in claim 1 , wherein the second network entity is connected to the application server via at least one of a Call State Control Function (CSCF) unit and an Interconnection Border Control Function (IBCF) unit.

7. The method as claimed in claim 1 , wherein the at least one SIP service is a calling service.

8. The method as claimed in claim 7 , wherein the first access node and the second access node are based on the Voice over Internet Protocol (VoIP).

9. The method as claimed in claim 1 , wherein the at least one telephone system checks, dynamically, connectivity with the first network entity via the first access node at regular interval of time.

10. A system comprising non-transitory computer-readable storage medium storing one or more sequences of instructions which, instructions executed by one or more processors cause the system to provide at least one SIP trunk service to at least one telephone system by an application server over a network, the system comprising:

the application server connected to the network via at least one network entity and configured to provide the at least one SIP trunk service to the at least one telephone system over the network;

the at least one network entity connected to the application server and configured to route the at least one SIP trunk service to the at least telephone system;

at least one telephone system configured to:

establish a connection with a first network entity of the network via a first access node wherein the first network entity is a Primary Enterprise Access Session Border Controller (PR-ESBC); and

avail at least one SIP trunk service, via the first access node, from the application server connected to the first network entity;

check, dynamically, connectivity with the first network entity via the first access node;

establish a connection with a second network entity of the network via a second access node, in an event the connectivity with the first network entity via the first access node fails, wherein the second network entity is a Secondary Enterprise Access Session Border Controller (GR-ESBC);

transmit a signaling request to avail the at least one SIP service, via the second access node, to the application server connected to the second network entity;

the application server further configured to:

process the signaling request received from the at least one telephone system via the second access node;

select a domain associated with the second network entity based on an identification of error code received from the at least one telephone system; and

provide the at least one SIP trunk service based on the selected domain to the at least one telephone system via the second access node; and

the at least one telephone system implements a configuration to avail at least one SIP trunk service, via the second access node, from the application server connected to the second network entity.